After completing cell search, the UE obtains the physical cell identifiers (PCI) of the current cell to resolve the master information blocks (MIBs) and system information blocks (SIBs). By performing MIB resolution, the UE acquires key information, including downlink (DL) synchronization and system bandwidth of the cell. It also detects the physical dedicated control channel (PDCCH) in the SIB time domain, and then obtains the System Information Block Type1 (SIB1) information based on the PDCCH before resolving other SIB information.
MIB Used in PLMN and Cell Selection.
The transmission period for MIBs is 40 ms. Within this period, the physical broadcast channel (PBCH) is located in subframe 0 of each radio frame and occupies the first four symbols of slot 2 within each subframe 0. Primary synchronization signals (PSSs) and secondary synchronization signals (SSSs) occupy 1.08 MHz in the center of the frequency domain, corresponding to the 6 resource blocks (RBs) in the middle of the frequency domain.
PLMN and Cell Selection: SIB1
The transmission period for SIB1 is 80 ms. The first transmission occurs in the radio frame numbered a multiple of 8 within a TTI (Transmission Time Interval), with repeated transmissions in other even-numbered radio frames within the TTI. Transmission is fixed on subframe 5 in the corresponding frame. The UE detects the PDCCH on these subframes. If there is a system information radio network temporary identity (SI-RNTI), the UE receives SIB1 on the physical dedicated sharing channel (PDSCH).
SIBn for PLMN and Cell Selection.
The transmission period for SIBn is a multiple of 80 ms. SIB2 contains radio resource-related configuration. SIBs 3 to 5 contain the cell reselection configuration for the LTE system. SIBs 6 to 8 contain the reselection configuration for UTRA, GERAN, and CDMA2000 systems. SIB9 contains the Home NodeB (HNB) configuration. SIB10 contains the primary earthquake and tsunami warning system (ETWS) notification, and SIB11 contains the secondary ETWS notification.
PLMN and Cell Selection.
SIB1 contains the public land mobile network (PLMN) table. The access stratum (AS) of the UE transmits the resolved PLMN table to the non-access stratum (NAS) of the UE. The NAS then selects an appropriate PLMN. After selecting a PLMN, the UE chooses an appropriate cell of the PLMN, camping on the cell with the strongest signal. This process ensures that the UE is connected to the most suitable network and can maintain reliable communication.
Read Also: How UE selects the appropriated PLMN?
By following these steps, the UE can effectively establish initial connectivity with the LTE network, enabling subsequent data communication and mobility management tasks.